Fuel dispensers are widely utilized to dispense fuels, such as gasoline, diesel, biofuels, blended fuels or the like, into the fuel tank of a vehicle. Many fueling nozzles include obstructions in the flow path that induce turbulence, vortices, and other turbulent eddy flows. For example, passages in the nozzle body, the interface between the nozzle body and the spout, and components in the spout such as an attitude device, sensing tube and sensing tube fitting may present obstructions. Regulatory recommendations and industry standards limit the length of the spout, and therefore the fuel is typically unable to dissipate the effects of these obstructions and reach a uniform flow pattern prior to exiting the spout.
The turbulent flow of fuel exiting the nozzle can present various difficulties. For example, many nozzles utilize an automatic shut-off device which includes a sensing port positioned near the end of the spout. A poor spray pattern of fuel exiting the nozzle can cause splash back of the fuel from the walls of the vehicle fill pipe. The splash back can reach the sensing port of the shut-off device, thereby causing nuisance shut offs. Existing fuel dispensers may also allow fluid to wick upwardly along the underside of the spout, which can also cause nuisance shut offs.
Turbulent flow and/or poor spray patterns of fuel exiting the nozzle can also affect the performance of the system when refueling vehicles which include an onboard refueling vapor recovery (“ORVR”) system. In particular, liquid seal ORVR systems are typically designed such that the vehicle fill pipe has a progressively reduced inner diameter. This configuration is provided so that fuel flowing into the fill pipe can cover or extend continuously across the cross section of the fill pipe, during refueling, to form a liquid seal which prevents fuel vapor from escaping through the fill pipe. The reduction in diameter of the fill pipe also causes a vacuum to be generated during refueling due to the venturi effect of the entering fuel stream.
Many fuel dispensers are configured to capture vapors emitted from a vehicle fuel tank during refueling, and return the vapors to the underground fuel storage tank. For example, stage II vacuum assist vapor recovery systems utilize a vapor pump to capture vapor and return the captured vapor through a vapor path of the fuel dispenser back to the ullage space of the underground fuel storage tank. Many stage II vacuum assist vapor recovery systems are configured to detect an ORVR-equipped vehicle, and cease operation of the vapor pump upon detection of an ORVR-equipped vehicle (i.e., if a vacuum is detected at the point of refueling, or at the end of the nozzle).
However, if fuel flow exiting the nozzle has sufficient turbulence and/or an undesirable spray pattern, the flow stream may jet toward the narrowed neck of an ORVR fill pipe in a non-uniform manner. In this case, the fuel may fail to extend continuously across the cross section of the fill pipe, which can cause the vehicle ORVR system to fail to generate a sufficient vacuum at the point of refueling. The fuel dispenser may thus fail to identify an ORVR-equipped vehicle as such. In this case, the vacuum pump of the fuel dispenser may continue to operate, which causes fresh air to be draw into the ullage space of the underground fuel storage tank. This fresh air causes excessive evaporation of the volatile fuels in the storage tank, which can cause pollutants to be released into the atmosphere by venting.